1. Field of the Invention
The present invention relates to a power distributing and synthesizing device, and more particularly to a power distributing and synthesizing device for distributing or synthesizing high-frequency microwave power in communication equipment.
2. Description of the Related Art
A Wilkinson type power distributing and synthesizing device which distributes or synthesizes high-frequency power in the microwave band, is disclosed in Japanese Unexamined Patent Application Publication No. 7-263993. This device has the advantages of both simplicity of circuit configuration and impedance conversion capability.
FIG. 8 is an equivalent circuit diagram of a conventional Wilkinson type power distributing and synthesizing device: The power distributing and synthesizing device 50 comprises first and second transmission lines 51 and 52, first, second and third signal terminals 531-533, a resistor 54, and capacitors 551-553. The connection portion between one end of the first transmission line 51 and one end of the second transmission line 52 is used as a first signal terminal (synthesis terminal) 531, the other terminal of the first transmission line 51 is used as a second signal terminal (distribution terminal) 532, and the other terminal of the second transmission line 52 is used as a third signal terminal (distribution terminal) 533. The second signal terminal 532 and the third signal terminal 533 are connected via the resistor 54. The first to third signal terminals 531-533 are connected to a ground via the capacitors 551-553.
When the power distributing and synthesizing device 50 is used as a distributor, a high-frequency signal is inputted to the first signal terminal 531, and the inputted high-frequency signal is outputted from the second and third signal terminals 532 and 533. On the other hand, when the power distributing and synthesizing device 50 is used as a synthesizer, high-frequency signals are inputted to the second and third signal terminals 532 and 533, and the inputted high-frequency signals are outputted from the first signal terminal 531.
Here, let the impedance of the circuit to be connected to the first signal terminal 531 be Z1, and the impedance of the circuits to be connected to the second and third signal terminals 532 and 533 be Z23. By setting the characteristic impedance of each of the first and second transmission lines 51 and 52 to (2xc2x7Z1xc2x7Z23)1/2, and the length of each of the first and second transmission lines 51 and 52 to xcex/4, impedance matching is realized between the power distributing and synthesizing device 50 and the circuits to be connected thereto. Also, by setting the characteristic impedance of the resistor 54 to 2xc2x7Z23, isolation between the second and third signal terminals 532 and 533 is realized.
However, in the above-described conventional power distributing and synthesizing device 50, since the first to third signal terminals are each connected to the ground via capacitors, it is impossible to remove high-frequency signals at a particular frequency although it is possible to remove higher harmonics of the high-frequency signal inputted to a signal terminal of the power distributing and synthesizing device. As a result, a filter, a trap, or the like needs to be connected to each signal terminal. This requires components for constructing the filters, and raises a problem of inhibiting the size-reduction of the power distributing and synthesizing device.
Furthermore, when the attenuation characteristics of the filter, the trap, or the like to be connected to each of the signal terminals is insufficient, problems occur, in that the isolation between the synthesis terminal and the distribution terminals deteriorates, and that thereby the performance of communication equipment using this power distributing and synthesizing device also deteriorates.
The present invention is able to solve such problems associated with the conventional art, and to provide a power distributing and synthesizing device capable of removing high-frequency signals at a particular frequency, and at the same time capable of sufficiently securing isolation between the synthesis terminal and the distribution terminals.
To solve the above-described problems, the present invention provides in its first aspect a power distributing and synthesizing device comprising first and second transmission lines; a synthesis terminal constituted of the connection portion between one end of the first transmission line and one end of the second transmission line; a first distribution terminal constituted of the other end of the first transmission line; a second distribution terminal constituted of the other end of the second transmission line; a resistor connected between the first distribution terminal and the second distribution terminal; and at least one LC serial resonator comprising an inductor and a capacitor. In this power distributing and synthesizing device, at least one terminal among the synthesis terminal, the first distribution terminal, and the second distribution terminal is connected to the ground via the at least one LC serial resonator.
Also, the present invention provides in its first aspect a power distributing and synthesizing device further comprising a laminated body formed by laminating a plurality of dielectric layers; strip line electrodes provided within the laminated body; and via hole electrodes provided within the laminated body. In this power distributing and synthesizing device, each of the first and second transmission lines is formed of the strip line electrodes; the inductor is formed of at least one of a strip line electrode and a via hole electrode; and the capacitor is formed of a plurality of electrodes formed within the laminated body so as to be opposed to each other across the dielectric layers.
The present invention provides in its second aspect a power distributing and synthesizing device comprising first and second transmission lines; a synthesis terminal constituted of the connection portion between one end of the first transmission line and one end of the second transmission line; a first distribution terminal constituted of the other end of the first transmission line; a second distribution terminal constituted of the other end of the second transmission line; a resistor connected between the first distribution terminal and the second distribution terminal; and at least one LC serial resonator comprising an inductor and a capacitor. In this power distributing and synthesizing device, a capacitor is connected in parallel with at least one of the first and second transmission lines.
Also, the present invention provides in its second aspect a power distributing and synthesizing device further comprising a laminated body formed by laminating a plurality of dielectric layers; and strip line electrodes provided within the laminated body. In this power distributing and synthesizing device, each of the first and second transmission lines is formed of the strip line electrodes; and the capacitor is formed of a plurality of electrodes formed within the laminated body so as to be opposed to each other across the dielectric layers.
Furthermore, in the power distributing and synthesizing device in according with the present invention, each of the strip line electrodes forming said first and second transmission lines may have a helical coil shape.
In the power distributing and synthesizing device in accordance with the first aspect of the present invention, since an LC serial resonator is connected between at least one terminal among the synthesis terminal, the first distribution terminal, and the second distribution terminal and the ground, it is possible to generate an attenuation pole by a serial resonance of the LC serial resonator, in the vicinity of the resonance frequency of an inputted signal. This allows high-frequency signals in the vicinity of the resonance frequency to be removed.
In the power distributing and synthesizing device in accordance with the second aspect of the present invention, since a capacitor is connected in parallel with at least one of the first and second transmission lines, it is possible to generate an attenuation pole by a parallel resonance of the LC parallel resonator comprising at least one of the first and second transmission lines and a capacitor, in the vicinity of the resonance frequency of an inputted signal. This allows high-frequency signals in the vicinity of the resonance frequency to be removed.
The mobile communication equipment in accordance with the present invention uses the above-described power distributing and synthesizing device.
In the mobile communication equipment in accordance with the present invention, since the power distributing and synthesizing device is capable of securing sufficient isolation between the synthesis terminal and the distribution terminals, and allows a cost reduction and a reduction in size, it is possible to achieve a small-sized transmitter which is superior in characteristics.
The above and other features and advantages of the present invention will be apparent from the following detailed description of several embodiments of the invention in conjunction with the accompanying drawings.